1. Field of the Invention
This invention relates to an illuminating device for a scanner, and to a print reading apparatus.
2. Description of the Related Art
A print reading apparatus is used, for example, to control the feed rate of ink and the feed rate of dampening water in a printing press based on image data of prints, and to inspect printed images. The print reading apparatus is the scan type that moves a print relative to an illuminating device and an image pickup device, and reads images from the print through the image pickup device while illuminating the print with the illuminating device (see Japanese Unexamined Patent Publication 2002-355950, for example).
Such a scan type print reading apparatus uses light sources in the form of long tubes such as fluorescent lamps. In order to use efficiently the light emitted from the light sources in the form of long tubes, the illuminating device includes reflectors such as concave mirrors disposed at the back of the light sources.
The illuminating device used in such a print reading apparatus is required to illuminate a print with a linearly uniform light of high illuminance. In the conventional illuminating device, the reflectors condense the light in directions perpendicular to the axes of the tubular light sources. However, little or no consideration has been made as to a condensation of light axially of the tubular light sources. Thus, where the tubular light sources such as fluorescent lamps are used, illuminance is high in a region corresponding to a middle portion longitudinally of each light source, and low in regions corresponding to opposite ends thereof